Keyboard actuated rhythm accompaniment



United States Patent 3,520,984 KEYBOARD ACTUATED RHYTHM ACCOMPANIMENTWilliam V. Machanian, North Tonawanda, N.Y., assignor to The WurlitzerCompany, Chicago, 11]., a corporation of Ohio Filed May 18, 1967, Ser.No. 639,518 Int. Cl. Gh U00, U02

US. Cl. 84-1.24 9 Claims ABSTRACT OF THE DISCLOSURE Electronic circuitsforming a part of an electronic organ for producing percussive tonessuch as drums, blocks, brushes, cymbals and the like, concurrently withthe musical or melody notes and keyed by the keys of the manuals and bythe pedals.

It is common practice to provide small dance bands or musicalcombinations for producing or playing popular music for dancing or forentertainment. One or more instruments may be used to play the melody,and, in addition, there preferably is a rhythm accompaniment, producedby one or more musicians operating with various percussive type soundgenerators, such as drums, blocks, brushes, cymbals, and the like. Suchrhythm accompaniment is of a repetitive nature, differing in accordancewith the nature of the music, i.e., fox-trot, samba, cha-cha, etc.

Often a small club or the like simply cannot afford the expense of morethan one musician. This musician will often play an electronic organ,since it provides the most versatile effects. In order to provide thehighly desirable rhythm accompaniment, various rhythm devices have beendeveloped, and insofar as I am aware, the first of these was soldcommercially by The Wurlitzer Company and known as the Sideman rhythmdevice. This device is disclosed and claimed in US. Letters Patent No.3,207,835 in the names of Holman, Hearne, and Korinke, and it further isdisclosed and claimed in Joseph H. Hearne patent application for RhythmDevice, Ser. No. 580,504, now Pat. No. 3,358,069, filed Sept. 19, 1966.The Sideman rhythm device referred to is a separate unit.

In order to conserve space, and to produce results in strict conformitywith a players timing, and for other desirable purposes, furtheradvances were made wherein electronic generators simulating the soundsof drums, blocks, cymbals, etc. wereincorporated as added-on, built-inparts of an electronic organ, sold by The Wurlitzer Company under thetrademark Ssh-boom. This latter device is disclosed and claimed inJoseph H. Hearne application Ser. No. 341,080, now Pat. No. 3,317,649,filed Jan. 29, 1964, for Manual Control of Electronic PercussionGenerated With Organ, allowed on Dec. 16, 1966, and in Harold O.Schwartz and Peter E. Maher application Ser. No. 448,362, now Pat. No.3,340,344, filed Apr. 15, 1965 for Transistorized Electronic PercussionGenerator With Organ.

The present invention is concerned with a built-in electronic percussiongenerator forming a part of an electronic organ, generally similar tothat just outlined. It is an object of the present invention to provideimproved means for keying or gating the various percussion soundoscillations.

It is a further object of the present invention to provide improved(means for modulating a hissing sound to simulate the shimmer of acymbal.

It is another object of the present invention to produce a built-inpercussion accompaniment better adapted for mass production andrequiring less in the way of selected components.

Still another object of the present invention is to provide switching orgating means in percussion generator circuits in an electronic organwhich operate more rapidly than in the past.

Other and further objects and advantages of the present invention willbe apparent from the following description when taken in connection withthe accompanying drawings wherein:

FIG. 1 is a perspective view of an organ constructed in accordance withthe present invention;

FIG. 2 is a block diagram corresponding to certain parts of the presentinvention;

FIG. 3a is a partial Wiring diagram of the improved percussion generatorcircuits; and

FIG. 3b comprises the remainder of the percussion circuit wiringdiagram, and is to be considered in conjunction with FIG. 3a.

Turning now in greater particularity to the drawings, and first to FIG.1, there will be seen an electronic organ generally designated by thenumeral 10 and including an upper keyboard or manual 12, and a lowerkeyboard or manual 14, along with a plurality of stop tablets 16. Theorgan also includes a pedalboard or clavier 17, a loudspeaker system 18which may be complex (as is known in the art), and a swell pedal 20 forcontrolling the overall volume of the organ.

The electronic circuits of the organ are indicated schematically in FIG.2, and include a plurality of organ tone generators 22. These organ tonegenerators may be of any well-known type, including transistoroscillators. The generators preferably are of the constantly oscillatingtype, and are respectively connected to key switches 24 operated by thekeys for pedals of the keyboards 12 and 14 and the pedalboard 17 to stopswitches and filters indicated collectively at 26, these stop switchesbeing operated by the stop tablets 16. Connection is then made through apreamplifier 28 to an organ amplifier 30, and hence to the loudspeaker18, which, as indicated previously, can be rather complex in nature.

The organ circuits also include a noise generator and amplifier,indicated generally at 32. This is connected through a diode 34 to ajunction point 36. The junction is connected through a diode 38 to ajunction 40, and on through a capacitor 42 to a junction 44. A brushkeyer 46 is connected through a resistor 48 to the junction 40.

Connection is made from the junction 36 through a diode 50 to a junction52, and from thence through a capacitor 54 to the junction 44. A cymbalkeyer 56 is connected through a resistor 58 to the junction 52.

Connection is made from the junction 44 through a junction 60 to noiseoutput amplifier and filter 62. A shimmer generator 64 is connectedthrough a resistor 66 to the junction 60. The noise output amplifier andfilter 62 is connected to the amplifier 30 through a resistor 68.

A drum generator 70 also is connected to the amplifier 30 through aresistor 62, and is under the control of a drum keyer 74.

A brief functional description of operation is believed in order at thispoint to facilitate understanding of the complete wiring diagram tofollow hereinafter. Thus, each time one of the key switches 24 of akeyboard 12 or 14 is operated to produce an appropriate musical melodytone, the cymbal keyer 56 or brush keyer 46, or both, depending on thesetting of appropriate stop tablets 16, is operated. The diodes 34, 38and 50 are normally biased 01f. As will be appreciated, the diodes 34and 38 are in series, thereby greatly increasing isolation over a singlediode, and likewise the diode 34 is in series with the diode 50. If thebrush keyer 46 is operated, the

diodes 38 and 34 are biased on to conduct a noise signal from the noisegenerator and amplifier 32 to the noise output amplifier and filter 62.The circuits are such as to simulate the sound of a cymbal that isstruck with a brush. n the other hand, if the cymbal keyer 56 isoperated, the diode 50. If the brush keyer 46 is operated, the signal tosimulate a cymbal struck as by a drum stick.

An amplified noise signal simply by itself is somewhat of a hissingsound, and therefore is not quite an accurate representation of acymbal. However, the shimmer generator operates at a frequency justslightly below the audio range, and amplitude modulates the noisesignal, thereby to provide a more realistic cymbal sound.

Each time a key switch 24 is closed by depression of a pedal 16, thedrum keyer 74 is operated to cause the drum generator to produce adrum-like sound. In a specific drum circuit to follow hereinafter, thedrum generator is a damped oscillator that is normally biased short ofoscillation. The drum keyer provides a potential pulse that momentarilybiases the generator into oscillation, which oscillation decays rapidly.Obviously, it would be fully equivalent to provide a continuouslyoperating generator for the drum signal, and to open a gate rathersuddenly and then to close it in decaying fashion to simulate the drumsound. The pedal switches also are capable of operating the cymbalkeyer.

FIGS. 3a and 3b should be considered, with both disposed horizontallyand FIG. 3b disposed immediately above FIG. 3a. Certain of the wiresextend from one figure to another, and these are respectively labeled Athrough H on both figures. It will be understood that these arecontinuous, and have been broken only for the sake of placing thedrawing on two sheets to make it large enough.

Referring now to the upper left portion of FIG. 3b, the keyboards 12 and14 are partially represented diagrammatically by a broken linerectangle. Included therein is a positive voltage source, indicated atB+ as a supply bus 76, connected through a resistor to a distributionbus 82 shunted by a filter comprising capacitor 84 and resistor 86.Collector rods or buses 88 of the upper manual are respectivelyconnected through resistors 90 to a collector 92. The collector 92 isconnected through a resistor 94 to the bus 82, and it also is connectedthrough a capacitor 96 to a line 98. A few of the key switches 100 ofthe upper manual are shown diagrammatically. Each is grounded and isnormally spaced out of contact with the adjacent bus 88. The keyswitches 100 are selectively closed against their cooperating busesWhenever a respective key is depressed.

Similarly, as to the lower manual, there is a collector 102 connectedthrough a resistor 104 to the bus 82, and also connected through acapacitor 106 to a line 108. The key switches 110 of the lower manuallikewise are grounded, and are normally spaced from, but are engageablewith the collector buses or bus rods 112 upon depression of acorreponding key, the buses being connected through resistors 114 to thecollector 102.

It will be understood that there is a voltage divider action among theresistor 80, the resistor 94, and the various resistors 90. (Similarly,there is a voltage divider action among resistor 80, resistor 104, andresistors 114.) Thus, whenever one of the switches 100 is closed, thevoltage divider action causes the potential on the collector 92 to dropfrom the B+ potential on the line 76 to some lower value, and thuscauses a negative pulse to be transmitted by the capacitor 96. If onekey switch is held down, and another is depressed, then two resistors 90are connected in parallel, again somewhat dropping the voltage on thecollector 92 and sending another negative pulse through the capacitor96. These negative pulses are used for keying purposes, as will bebrought out shortly hereinafter. As will be understood, the samesituation pertains with regard to the key switches 110 of the lowermanual 14.

The line 98 leads from FIG. 3b to FIG. 3a to a diode 116 paralleled by aresistor 118. The diode 116 is poled so as to pass negative pulses, butnot any possible pulses or disturbances of a positive polarity. Theother side of the diode is connected to a stop tablet switch 120 whichis operated by one of the stop tablets 16, specifically the one numberedin FIG. 3a as 161 and labeled SSH- BOOM UPPER. The other side of theswitch 120 is connected to a collector 122 which leads through aconnecting line 124 to the input of the brush keyer 46. The negativepulse applied at the input to the brush keyer is indicated above theline 124 and to the left of the brush keyer at 126.

The line 108 also extends from FIG. 31; down onto FIG. 3a to a switch128, this being controlled by one of the stop tablets 16, specificallynumbered as 162 and labeled SSH-BOOM LOWER. This switch is alsoconnected to the line 124.

The line 122 is connected through a capacitor to a normally open switch132 which is closed by means of one of the stop tablets 16, specificallynumbered as 163 and labeled SSH-BOOM PEDAL CYMBAL. The other side of theswitch 132 is connected to a line 134. The line 134 is connected througha resistor 136 to a positive voltage source indicated at B+. Connectionis made to the line 134 by a normally open switch 140 grounded through aresistor 138. The switch 140 is arranged to be closed whenever one ofthe pedals 17 is depressed, and this, for example, can be done by meansof a, well-known bail which is pivoted whenever any pedal is depressed,whereby to close the switch 140. Thus, the voltage appearing on the line134 is dropped *any time the switch 140 is closed, thereby causing anegative pulse or spike to 'be passed by the capacitor 130 to the line24. As will be understood, it is normal for the pedal notes to be playedonly one at a time, and hence it is only necessary to provide one switch140.

A second switch 142 is also closed by depression of any pedal 16, andthis switch is connected through a resistor 144 to a positive voltage,but of lower potential than the B+ supply. The switch 142 may be gangedwith the switch 140, and is so shown. The opposite side of the switch142 leads through a line 146 to a line 148, and this in turn leads to astop tablet controlled switch 150 which is ganged with the switch 132for closure by the stop tablet 16-3. The other side of the switch 150 isconnected to a line 152, and this line passes through a diode 154 inseries with a resistor 156, shunted to ground by a capacitor 158, to aline 160, about which more will be said shortly. However, it will beapparent that with the switch 150 closed, whenever the pedal switch 142is closed a positive voltage is applied through the diode 154 to theline 160. This positive voltage is used for keying, as will be broughtout shortly.

Attention now should be directed to the upper portion of FIG. 3b whereinthe brush keyer 46 is shown in detail. The line 124 is connected to thebase of a transistor 162, the base being connected to ground by aresistor 164 paralleled by a capacitor 166. The transistor is of then-p-n type, and has the collector thereof connected through a resistor168 to a positive potential line 170. The base of this transistor alsois connected through a resistor 172 to the line 170, thereby servingwith the resistor 164 as a voltage divider biasing the base. The emitteris connected to ground through a resistor 174 paralleled by a capacitor176. The transistor 162 and associated components will be recognized asbeing an amplifier which amplifies and inverts the pulse 126.

The collector of the transistor 162 is also connected to the base of atransistor 178, also of the n-p-n type, and having the collector thereofconnected direct to the positive supply line 170. The emitter isconnected to ground through a resistor 180, and is also connected to adiode 182. The transistor 178 will be recognized as anemitter followerbuffer amplifier, and the output pulse thereof is positive as indicatedat 184, being sharpened 'and amplified. The diode 182 is poled to passpositive pulses.

The diode 182 is connected to a resistor 186, the junction between thediode and resistor being shunted to ground by a rather small capacitor188. The output side of the resistor 186 also is shunted to ground by arelatively small capacitor 190, and also is connected to the resistor 48previously mentioned. The capacitors and resistors just mentioned maynot in every instance be necessary, but are desirable in some organs toslow the attack somewhat, and thereby to avoid adverse interaction witha reverberation unit.

The noise generator and amplifier 32 includes an n-p-n transistor 192having the base thereof grounded, and having the emitter thereofconnected through a resistor 194 to a positive voltage supply line 196.The collector is not connected, and the base and emitter serve as adiode biased to its Zener point to produce a noise output. A droppingresistor 198 connects the positive voltage supply line 196 to thepreviously mentioned voltage supply line 170.

The output of the Zener biased transistor 192 is connected through acapacitor 200 to the base of an n-p-n transistor 202. The collector ofthis transistor is connected through a resistor 204 to the positivevoltage line 170, and the line 170 is connected to a biasing resistor206 which is connected to the base of the transistor 202, and also to agrounded resistor 208, the resistors 206 and 208 determining the bias ofthe base. The emitter is connected to a resistor 210 paralleled by acapacitor 212, and this parallel combination is grounded through aresistor 214. Ideally, the resistor 214 would not be required, but thisresistor is of selected, rather small value to compensate for othertolerances in the circuit to produce the desired output.

As will be appreciated, the transistor 202 and associated circuitelements comprise an amplifier for the noise generated by theZener-connected transistor 192, and the output of the transistor stage202 is taken from the collector, being connected through a capacitor 216to the base of a following n-p-n transistor 218. The collector again isconnected through a resistor 220 to the voltage supply line 170, andvoltage divider resistors 222 and 224 provide bias for the base, theresistor 224 being shunted by a capacitor 226. The emitter is groundedthrough a resistor 228 and parallel capacitor 230, and the output isconnected through a filter 232 comprising a series resistor 234paralleled by a capacitor 236, the input side of this parallelcombination being shunted to ground by capacitor 238. The output side isconnected to the diode 34.

The junction point 36 is connected to the diode 34 as previously stated,and is shunted to ground by a capacitor 240. It is also connected to thediodes 38 and 50 as previously stated, the diode 38 being connectedthrough the capacitor 42 to the junction 44, with the intermediatejunction 40 being grounded through a resistor 242. Similarly, theintermediate junction 52 is grounded through a resistor 244, and isconnected to the capacitor 54, as previously noted. The capacitor 54 isconnected through a resistor 246 to the base of a transistor 248 forminga part of the noise output amplifier and filter. The collector of thistransistor is connected through a resistor 250 to the positive voltageline 170, while the base is biased by voltage divider resistors 252 and254 connected between the line 170 and ground. The emitter is groundedby a resistor 256 paralleled by a capacitor 258.

The output of the transistor amplifier stage employing the transistor248 is taken from the collector through a capacitor 260 which leadsthrough a resistor 262 to a shunting tank or tuned circuit comprisingparallel connected inductance 264 and capacitor 266. Connection iscontinued through a series resistor 268 and a shunting capacitor 270 toa junction 272. The junction 272 is connected through a series resistor274 and a grounded shunting resistor 276 to the resistor 68 previouslymentioned.

Reference now should be made to the shimmer generator 64 at the upperleft portion of FIG. 3a. Connection is made to the D generator at 294cycles as indicated at 278, and this connection goes through a resistor280 to a junction 282. Connection also is made at 284 to the adjacent D#generator at 311 cycles per second, and from this connection theresistor 286 leads to the junction 282. Connection is made from thejunction 282 through a capacitor 288 to the base of an n-p-n transistor290, the collector of which is connected through a resistor 292 to thepositive voltage supply line 170. The base is connected to ground by aresistor 294, and the emitter is also connected to ground by a resistor296. The transistor is biased off, and the base to emitter section actsas a diode detector. The sum and difference frequencies are detected,and the output of the transistor, taken from the collector, is appliedto a roll-oif filter to eliminate frequencies of 294 cycles per secondand above. The filter includes a shunting capacitor 298, and a resistor300* connected to the emitter by a coupling capacitor 302. The outputside of the resistor 300 is shunted to ground by a capacitor 303, and isalso connected through the resistor 66 and a line 304 to the junction44. Only the 17-cycle per second difference frequency comes through tothe base of the transistor 248, and this 17-cycle per second frequencyamplitude modulates the noise signal applied to the base of thetransistor 248, thereby to produce a shimmering effect simulating amechanical cymbal.

The drum generator 70- comprises a phase shift oscillator 'which isbiased short of oscillation. It includes an n-p-n transistor 306, theemitter of which is connected to a junction 308 leading through aresistor 3 10 and a decoupling filter comprising series resistor 312 andshunting capacitor 314 to the positive voltage supply line 170. Avoltage divider resistor 316 is connected to the top of the resistor310, and at the opposite end is connected to the base of the transistor306, the base also being connected through another voltage dividerresistor 318 to ground. Series capacitors 320 and 322 also are connectedin series to the base, and the junction between these two capacitors isgrounded through a resistor 324. The far end of the capacitor 322 isconnected through a resistor 326 to a junction 328, the latter beinggrounded through a resistor 330, and also connected to a resistor 332.The resistor 332 is connected to a junction 334, grounded through acapacitor 336, and connected through a diode 338 to a junction 340, thelatter being grounded through a resistor 342 and connected through acapacitor 344 to a line 346. A feed-back capacitor 348 is connected fromthe collector of the transistor 306 to the junction between thecapacitor 322 and the resistor 326 in a phase shift oscillatorconnection.

The line 346- is connected to a switch 350 operated by a SSH-BOOM PEDALDRUM stop tablet 16-4. When this switch 350 is closed, closure of theswitch 142 applies positive potential to the line 346, which passes apositive pulse through the capacitor 344, and through the diode 338 tobias the phase shift oscillator of the drum generator for oscillation.Since the capacitor 344 passes only a pulse, the bias immediately startsto decay as the capacitor 336 is initially charged and subsequentlydecays through resistors 332 and 330, whereby the oscillations decay inthe manner of a struck drum. The diode 338 prevents the capacitor 336from discharging backwards into the source. Diodes 154 and 182 servesimilar purposes.

The emitter of the transistor 306 is grounded through a resistor 352shunted by a capacitor 354. The junction 308 on the collector isconnected through a coupling capacitor 356 and a series resistor 358 toa junction 360 shunted to ground by a capacitor 362. The junction alsois connected to a line 364 which leads to a movable switch contact 368of a switch 366. The movable switch contact normally engages a fixedswitch contact 370 connected to the junction 372 between seriesresistors 374 and 376, the latter of which has the bottom end thereofgrounded. The top end of the resistor 374 is connected to a line 378.Another fixed switch contact 380 engageable by the movable contact 368is connected direct to the line 378. The position of the switch contact368 is determined by one of the stop tablets 16, namely, a NORMALSSH-BOOM VOLUME-FUL stop tablet 165. The movable contact 368 engages thefixed contact 370 for the normal position, and there is some attenuationthrough the voltage divider action of the resistors 374 and 376. Withthe stop tablet moved to the FULL position, the movable contact engagesthe fixed contact 380, and there is no attenuation.

There is a second movable contact 382 which is normally engageable witha fixed contact 384. This fixed contact is connected through a resistor386 to ground. The movable contact 382 is ganged with the movablecontact 368, and is moved from the fixed contact 384 by movement of thestop tablet 16-5 from its normal to its full position.

The movable contact 382 is connected to a line 388 leading to a junction390, and hence to the junction 272 on the output side of the noiseoutput amplifier and filter. Thus, in the normal position of the stoptablet 16-5, the resistor 386 shunts the output of this noise outputamplifier and filter, and with the movable switch contact 382 raisedthere is no such shunting, thus raising the volume level.

The junction 390 also is connected by a line 392 to a movable switchcontact 394 normally engageable with the grounded fixed switch contact396. A movable switch contact 398 is ganged with a fixed switch contact400, which also is grounded. The movable switch contact 398 is connectedto the wire 378. Both of the movable contacts 394 and 398 are gangedtogether and are controlled by a SSH-BOOM OFF-ON stop tablet 16-6. Withthe stop tablet 16-6 in the OFF position, the movable contacts 394 and398 engage their respective fixed grounded contacts, and thereby shuntthe drum generator and the noise output amplifier and filter outputs toground. Conversely, when the stop tablet 16-6 is moved to the ONposition, the grounding shunt is removed, and the full output of theamplifier is passed.

Various output connections are shown at the upper right corner of FIG.3a. Thus, a line 402 leads from the resistor 68 and goes to theamplifier 30, preferably through a preamplifier stage to provide an outof phase relationship at a reverberation unit, and thereby to preventunfavorable reaction thereon. Alternatively, it can, of course, go to anentirely separate amplifier and loudspeaker system.

Similarly the line 388 is connected through a line 404 to a resistor 406leading to a junction 408, and onto the amplifier 30.

In like manner, the line 378 leads to a junction 410 which is connectedthrough a cross-over resistor 412 to the junction 408. The resistor 410-also is connected through a series resistor 414 leading to theamplifier.

OPERATION Portions of the operation of the present invention have beenset forth heretofore. However, in order to put everything in one placeas to operation, and with reference to FIG. 2 and also FIGS. 3a and 3b,closure of any key switch 100 of the upper manual or of a key switch 110of the lower manual, with the appropriate stop tablets 16-1 and 162closed, a negative pulse will be transmitted to the brush keyer 46. Thiswill apply a positive pulse to the junction 40, and bias both diodes 34and 38 for conduction momentarily. The noise signal generated by thenoise generator amplifier 32 will be passed briefly as somewhat of ahissing sound, but amplitude modulated by the shimmer generator 64,whereby to produce a momentary cymbal sound, specifically of a cymbalstruck lightly with a wire brush.

The upper manual path includes the diode 116, whereas there is no suchdiode in the lower manual path. This is not significant relative to thepresent circuit, but is provided to prevent notes played on the lowermanual, with both upper and lower SSH-BOOM" stop tablets operated, fromfeeding back to the upper manual to cause false operation of othercircuits. The resistor 118 paralleling the diode is to provide fordischarge of capacitors when the diode is not conducting.

When any pedal note is played with the stop tablet 16-3, SSH-BOOM PEDALCYMBAL, actuated, a negative pulse again will be transmitted to thebrush keyer 46, to produce the same action as just described. At thesame time, a positive potential will be applied to the line 152, andthrough the diode 154 to junction 52, whereby to turn on diodes 50' and34. These diodes will remain turned on as long as the pedal is helddown. When the pedal is released, the capacitor 158 will dischargethrough the resistor 156 to provide a decay. Thus, a tone is producedthat is similar to a crash cymbal, i.e., a cymbal struckwith a drumstick or the like. Also, if the SSH- BOOM PEDAL DRUM stop tablet 164 isin operating position, playing of a pedal note will apply a potential tothe line 346, which will be in the nature of a pulse through thecapacitor 344 and diode 338 to turn on the drum generator in a decayingfashion to produce a thump similar to that of a bass drum.

4 It will be observed that the brush keyer is quick acting, andtherefore produces a brush sound simultaneously with the playing of amusical or melody note. The diode gates for the brush and cymbal areinexpensive and reliable in operation. Using the two diodes in seriesreduces leakage noise by a factor of at least ten over a transistor gateusing a single transistor. Although turning on of one of the diodes 38or 50 turns on the diode 34, thereby leaving only one diode to block inthe other path, a higher noise level can be tolerated at this time,since it will be masked by the sound being produced.

Although reference has been made heretofore to brush and cymbal, it willbe understood that both are sounds as produced by a cymbal, the formeras when a cymbal is lightly actuated by a wire brush, and the latter aswhen a cymbal is struck by a drum stick or the like. Hence the termcymbal is used generically in the claims. Similarly, a pedal is a keyoperated by the foot, and key is intended in a generic sense to cover apedal as well as a manually operated key.

With reference to the shimmer generator 64, it will be noted that thegeneration of the shimmer frequency by the detecting of a differencesignal and filtering out of the sum frequency eliminates the necessityof a separate tone generator, and in particular eliminates the need forproviding some means of frequency stabilization for the shimmergenerator.

The specific example of the invention as herein shown and described isby way of example. Various changes in structure may occur to thoseskilled in the art, and will be understood as forming a part of thepresent invention insofar as they fall within the spirit and scope ofthe appended claims.

The invention is claimed as follows:

1. An electronic rhythm percussion accompaniment system comprising akeyboard musical instrument having a plurality of keys, a plurality ofkey switch means selectively closed thereby, a plurality of music tonegenerators respectively operated by said keys for playing music, meansfor generating a wide spectrum of audio frequency electrical noise,diode means connected to said noise generating means, electronic outputmeans connected to said diode means for producing a cymbal type toneupon conduction of said diode means, said diode means being normallybiased off, and means connecting said key switch means and said diodemeans for rendering said diode means conductive upon closure of said keyswitch means, said diode means comprising two diodes forming parallelpaths between said noise generating means and said output means, therebeing separate means connecting key switch means to each of said twodiodes for respectively rendering said diodes conductive.

2. A system as set forth in claim 1 and further including a third diodein series with each of said first two diodes and with said noisegenerating means, and rendered conductive by interaction with either ofthe first two diodes rendered conductive.

3. A system as set forth in claim 1 wherein the means interconnectingsaid key switch means and said diode means includes means for deliveringa pulse to said diode means to render said diode means only momentarilyconductive.

4. A system as set forth in claim 1 wherein the means interconnectingsaid key switch means and one of said diodes includes means fordelivering a pulse only momentarily to render that diode conductive, andthe means interconnecting the key switch means and the other diodeincludes means for rendering the other diode continuously conductive fora predetermined time.

5. A system as set forth in claim 4 wherein said diode means furtherincludes a third diode in series with each of said first two dides andwith said noise generating means, said third diode being normallynon-conductive and rendered conductive upon conduction of either of saidfirst two diodes.

6. A system as set forth in claim 1 and further including means forproviding a low frequency oscillation, and means interconnecting saidoscillation providing means and said diode means for amplitudemodulating the noise signal passed by said diode means.

7. An electronic rhythm percussion accompaniment system comprising akeyboard musical instrument having a plurality of keys, a plurality ofkey switch means selectively closed thereby, a plurality of music tonegenerators respectively operated by said keys for playing music, meansfor generating a wide spectrum of audio frequency electrical noise,diode means connected to said noise generating means, electronic outputmeans connected to said diode means for producing a cymbal type toneupon conduction of said diode means, said diode means being normallybiased off, means connecting said key switch means and said diode meansfor rendering said diode means conductive upon closure of said keyswitch means, means for providing a low frequency oscillation, and meansinterconnecting said oscillation providing means and said diode meansfor amplitude modulating the noise signal passed by said diode means,

the low frequency oscillation providing means comprising a pair of tonegenerators differing in frequency, a detector circuit connected to bothsaid tone generators for detecting the sum and difference frequencythereof, and filter means for eliminating said two frequencies and thesum frequency and passing only the difference frequency.

8. An electronic organ rhythm percussion accompaniment system comprisingan electronic organ having a plurality of keys, a plurality of keyswitch means selectively closed by said keys, a plurality of organ tonegenerators respectively controlled by said key switch means for playingmusic, organ output means including amplifier means connected to saidgenerators and said key switch means for reproducing such music, meansfor generating a wide spectrum of audio frequency electrical noise, gatemeans connected to said noise generating means and to said output meansfor producing a cymbal type tone upon opening of said gate means, saidgate means being normally non-conductive, means for comparing thefrequencies of two adjacent ones of said organ tone generators, filtermeans for eliminating all but the difference frequency, meansinterconnecting said filter means and said gate means for amplitudemodulating noise signals passed by said gate means, and meansinterconnecting said key switch means and said gate means for renderingsaid gate means conductive upon closure of said key switch means.

9. An electronic organ rhythm percussion accompaniment system as setforth in claim 8 wherein the frequency comparing means includesdetecting means for detecting the sum and difference frequencies.

References Cited UNITED STATES PATENTS 2,783,672 3/1957 Hanert 84l.263,291,886 12/1966 Tinker 841.01 3,297,812 1/1967 Cordry 84l.0l 3,340,3449/1967 Schwartz et al. 84l.25 XR 3,389,211 6/1968 Slaats 841.0l

FOREIGN PATENTS 951,169 3/1964 Great Britain.

' ELI LIEBERMAN, Primary Examiner M. NUSSBAUM, Assistant Examiner US.Cl: X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 15522984 Dated July 21, 1970 Inventor(s) William V. Machanian It is certifiedthat error appears in the aboveidentified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 58, change "62" to --72-; Column 3, line 6, cancel theentire line and substitute:

--diodes 50 and 34 are turned on to conduct a noise-- Column 3, line 66,change "thus" to --this; Column 9, line 25, change "dides" to--diodes--.

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